Refactor: Move background image to main App composable and cleanup

This commit refactors the placement of the background image, moving it from `QuizScreen` to the main `KahootQuizApp` composable. This ensures the background is consistently applied across the app.

Additionally, this commit includes:
- Removal of unused Detekt configuration file (`ui/quiz/config/detekt/detekt.yml`).
- Minor code cleanup:
    - Removed commented-out code in `Theme.kt` and `Type.kt`.
    - Removed trailing blank lines in various domain model files.
    - Added `@file:Suppress("TooManyFunctions")` to `QuizMapper.kt`.
    - Added `@file:Suppress("MatchingDeclarationName")` to `QuizNavigation.kt`.
    - Used `1.seconds` instead of `1000` (Long) for delay in `QuizScreenViewModel`.

app/src/main/java/dev/adriankuta/kahootquiz/KahootQuizApp.kt

@@ -1,11 +1,16 @@
 package dev.adriankuta.kahootquiz
 
+import androidx.compose.foundation.Image
 import androidx.compose.foundation.layout.WindowInsets
+import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.safeDrawing
 import androidx.compose.material3.Scaffold
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.res.painterResource
+import dev.adriankuta.kahootquiz.core.designsystem.R as DesignR
 
 @Composable
 fun KahootQuizApp(
@@ -15,6 +20,12 @@ fun KahootQuizApp(
         contentWindowInsets = WindowInsets.safeDrawing,
         modifier = modifier,
     ) { paddingValues ->
-        KahootQuizNavGraph(modifier = modifier.padding(paddingValues))
+        Image(
+            painter = painterResource(id = DesignR.drawable.bg_image),
+            contentDescription = null,
+            contentScale = ContentScale.Crop,
+            modifier = Modifier.fillMaxSize(),
+        )
+        KahootQuizNavGraph(modifier = Modifier.padding(paddingValues))
     }
-}
+}

app/src/main/java/dev/adriankuta/kahootquiz/KahootQuizNavGraph.kt

@@ -20,4 +20,4 @@ fun KahootQuizNavGraph(
     ) {
         quizScreen()
     }
-}
+}